Dry Fiber Optic Cables and Assemblies

ABSTRACT

A fiber optic cable includes at least one optical fiber, at least one strength member, at least one dry insert, and a cable jacket. The cable jacket has a cavity with a generally rectangular cross-section with the at least one optical fiber and the at least one dry insert disposed therein. The at least one optical fiber has a predetermined level of coupling to the cable jacket that is provided by the at least one dry insert within the cavity of cable jacket. The predetermined level of coupling is about 0.1625 Newtons or more per optical fiber for a thirty meter length of fiber optic cable. Additionally, fiber optic cables of the present invention are also suitable as a portion of a cable assembly.

RELATED APPLICATIONS

This application is a Continuation of U.S. Ser. No. 12/277,963 filed onNov. 25, 2008, which is a Divisional of U.S. Ser. No. 11/643,357 filedon Dec. 21, 2006, now U.S. Pat. No. 7,471,862, which is aContinuation-In-Part (CIP) of U.S. Ser. No. 11/193,516 filed on Jul. 29,2005, now U.S. Pat. No. 7,415,181, all of which are incorporated hereinby reference.

TECHNICAL FIELD

The present invention relates generally to dry fiber optic cables andassemblies that are useful for routing optical fibers such as toward thesubscriber. Specifically, the fiber optic cables and assemblies of thepresent invention are useful as feeder cables, distribution cables, dropcables, and/or other suitable cables/assemblies in an optical network.

BACKGROUND

Communication networks are used to transport a variety of signals suchas voice, video, data transmission, and the like. Traditionalcommunication networks use copper wires in cables for transportinginformation and data. However, copper cables have drawbacks because theyare large, heavy, and can only transmit a relatively limited amount ofdata with a reasonable cable diameter. Consequently, optical waveguidecables replaced most of the copper cables in long-haul communicationnetwork links, thereby providing greater bandwidth capacity forlong-haul links. However, most communication networks still use coppercables for distribution and/or drop links on the subscriber side of thecentral office. In other words, subscribers have a limited amount ofavailable bandwidth due to the constraints of copper cables in thecommunication network. Stated another way, the copper cables are abottleneck that inhibit the subscriber from utilizing the relativelyhigh-bandwidth capacity of the optical fiber long-haul links.

As optical waveguides are deployed deeper into communication networks,subscribers will have access to increased bandwidth. But certainobstacles exist that make it challenging and/or expensive to routeoptical waveguides/optical cables closer to the subscriber. Forinstance, accessing optical waveguides and the connection between a dropcable and the distribution fiber optic cable require a low-cost solutionthat is craft-friendly for installation, connectorization, andversatility. Moreover, the reliability and robustness of the fiber opticcables and the interconnection therebetween must withstand the rigors ofan outdoor environment.

Conventional distribution fiber optic cables require opening by cuttingor otherwise splitting the cable jacket and pulling the optical fibersthrough the jacket opening. However, it can be difficult to locate thecorrect fibers, and even when they are located, removing them from thecable without damaging the selected optical fibers or other opticalfibers in the cable can be challenging. Once the desired optical fibersare located and safely removed, the operator has to connectorize orsplice the optical fibers for optical connection with the network.Conducting the access process with conventional cables inless-than-ideal conditions in the field is time-consuming, expensive,and risks damaging the optical fibers of conventional cables. Likewise,the access process is difficult in the factory with conventional cables.

SUMMARY

To achieve these and other advantages and in accordance with the purposeof the invention as embodied and broadly described herein, the inventionis directed in one aspect to a dry fiber optic cable that includes atleast one optical fiber, at least one strength member, at least one dryinsert, and a cable jacket. The cable jacket has a cavity with agenerally rectangular cross-section with the at least one optical fiberand the at least one dry insert disposed therein. The at least oneoptical fiber has a predetermined level of coupling to the cable jacketthat is provided by the at least one dry insert within the cavity ofcable jacket. The predetermined level of coupling is about 0.1625Newtons or more per optical fiber for a thirty meter length of fiberoptic cable.

In another aspect the invention is directed to a dry fiber optic cableincluding at least one optical fiber ribbon, a first dry insert, asecond dry insert, at least two strength members and a cable jacket. Thecable jacket includes a cavity with the at least one optical fiberribbon, the first dry insert, and the second dry insert disposedtherein. The two strength members are disposed on opposite sides of thecavity for providing tensile strength for the fiber optic cable. Thefirst dry insert and the second dry insert provide a predetermined levelof coupling of the at least one optical fiber ribbon to the cablejacket, wherein the predetermined level of coupling is about 0.1625Newtons or more per optical fiber for a thirty meter length of fiberoptic cable.

In another aspect the invention is directed to a fiber optic cableassembly including a dry distribution cable and a tether optical fibercable. The dry distribution cable includes at least one optical fiber,at least one strength member, and a cable jacket. The cable jacket has acavity and the at least one optical fiber is disposed within the cavity.The at least one optical fiber having a predetermined level of couplingto the cable jacket, wherein the predetermined level of coupling isabout 0.1625 Newtons or more per optical fiber for a thirty meter lengthof the distribution cable. The tether optical fiber cable has at leastone tether optical fiber with the tether optical fiber being in opticalcommunication with the at least one optical fiber of the distributioncable.

It is to be understood that both the foregoing general description andthe following detailed description present exemplary and explanatoryembodiments of the invention, and are intended to provide an overview orframework for understanding the nature and character of the invention asit is claimed. The accompanying drawings are included to provide afurther understanding of the invention, and are incorporated into andconstitute a part of this specification. The drawings illustrate variousexemplary embodiments of the invention, and together with thedescription, serve to explain the principles and operations of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an explanatory embodiment of a fiberoptic cable according to the present invention.

FIGS. 1 a-1 c depict cross-sectional views of exemplary optical fiberribbons suitable for use in the cables of the present invention.

FIG. 2 is a cross-sectional view of another explanatory fiber opticcable according to the present invention.

FIG. 3 is a cross-sectional view of still another explanatory fiberoptic cable according to the present invention.

FIGS. 3 a-3 d are cross-sectional views of alternate dry inserts for usewithin the cavity of the fiber optic cables according to the presentinvention.

FIG. 4 is a cross-sectional view of yet another explanatory fiber opticcable according to the present invention.

FIG. 5 is a cross-sectional view of another explanatory fiber opticcable according to the present invention.

FIG. 6 is a cross-sectional view of an explanatory fiber optic cablehaving a tearable portion for separating a portion of the cableaccording to the present invention.

FIGS. 7 and 7A are cross-sectional views of explanatory fiber opticcables having a plurality of cavities according to the presentinvention.

FIGS. 8 and 8A are cross-sectional views of explanatory fiber opticcables having an armored component according to the present invention.

FIGS. 9 and 10 respectively are a cross-sectional view and a perspectiveview of an explanatory fiber optic cable assembly according to thepresent invention.

FIG. 10 a depicts a perspective view of a portion the cable FIGS. 9 and10 after being opened and before the sealing portion is applied.

FIGS. 11 a and 11 b respectively depict schematic cross-sectional viewsof the fiber optic cable assembly of FIGS. 9 and 10 disposed within aduct and a schematic cross-sectional view of a fiber optic assemblyusing a round cable.

FIGS. 12 and 12 a respectively are a cross-sectional view and aperspective view of another fiber optic cable assembly according to thepresent invention.

FIG. 13 is a cross-sectional view of yet another fiber optic cableaccording to the present invention.

FIG. 14 is a schematic diagram illustrating a cross-section of a bendperformance optical fiber in accordance with an exemplary embodiment ofthe present invention.

FIG. 15 is a cross-sectional image of a microstructured bend performanceoptical fiber illustrating an annular hole-containing region comprisedof non-periodically disposed holes.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of theinvention, examples of which are described herein and shown in theaccompanying drawings. Whenever practical, the same reference numeralsare used throughout the drawings to refer to the same or similar partsor features. FIG. 1 depicts an exemplary fiber optic cable 10(hereinafter cable 10) according to the present invention that can beconfigured for use as a drop cable, a distribution cable, or othersuitable portions of an optical network. Generally speaking, adistribution cable will have a relatively high optical fiber count suchtwelve or more optical fibers for further distribution to the opticalnetwork. On the other hand, a drop cable will have a relatively lowoptical count such as up to four optical fibers for routing towards asubscriber or a business, but drop cables may include higher fibercounts. Cable 10 generally includes at least one optical fiber 12disposed as a portion of an optical fiber ribbon 13, at least onestrength member 14, and a cable jacket 18 having a cavity 20 configuredwith a generally flat profile. In other words, cables of the presentinvention have two major surfaces 11 that are generally flat and areconnected by arcuate end surfaces (not numbered) as shown, therebyresulting in a cable having a relatively small cross-sectionalfootprint. As best shown in FIGS. 1 a-1 c, at least one optical fiber 12is arrayed with a plurality of other optical fibers as a portion ofoptical fiber ribbon 13. Cable 10 also includes two strength members 14disposed on opposing sides of cavity 20, thereby imparting apreferential bend characteristic to cable 10. Strength members 14 arepreferably a dielectric material such as glass-reinforced plastic,thereby allowing an all dielectric cable design; however, strengthmembers may be a conductive material such as steel or the like. Cavity20 is sized for allowing ribbons 13 the adequate freedom to move when,for instance, the cable is bent while maintaining adequate opticalattenuation performance of the optical fibers within the cable. Simplystated, the cavity is not tightly drawn onto the optical fiber, butallows some movement. Additionally, jacket 18 may be formed from aflame-retardant material, thereby making it suitable for indoorapplications such as multi-dwelling units (MDUs).

Cable 10 is advantageous because it can be easily accessed from eitherof the generally planar sides of the cable, thereby allowing access tothe desired optical fiber. In other words, ribbons from either side ofthe ribbon stack, i.e., top or bottom, can be accessed by opening thecable at the respective planar side. Consequently, the craftsman is ableto access to any optical fiber desired for optical connection. Asdepicted, cavity 20 has a cavity minor dimension CH and a cavity majordimension CW and has a generally rectangular shape with a fixedorientation, but other shapes and arrangements are possible such asgenerally square, round, or oval. By way of example, cavity may berotated or stranded in any suitable manner along its longitudinallength. The cavity can also have a partial oscillation through a givenangle, for instance, the cavity can rotate between a clockwise anglethat is less than a full rotation and then rotate counter-clockwise forless than a full rotation. Furthermore, one or more cavities may beoffset towards one of the major surfaces 11, thereby allowing easyopening and access from one side as shown in FIG. 7 a.

As shown in FIG. 1, cavity minor dimension CH is generally aligned witha minor dimension H1 of distribution cable 10 and cavity major dimensionCW is generally aligned with the major dimension W1 of cable 10. Asdepicted, strength members 14 are disposed on opposite sides of cavity20 and are sized so that a strength member dimension D generally alignedwith minor dimension H1 of the cable is about the same size or smallerthan the cavity minor dimension CH. By way of example, cavity minordimension CH is sized so it is about five percent larger or more than astrength member dimension D that is generally aligned with minordimension H1 of the cable. Illustratively, strength member 14 is a roundglass-reinforced plastic (grp) having a diameter of about 2.3millimeters and cavity minor dimension CH is about 2.5 millimeters. Ofcourse, strength members 14 can have shapes other than round such as theoval strength members shown in FIG. 2.

Consequently, the craftsman or automation process has simple and easyaccess to cavity 20 by running a utility blade or cutting tool along thelength of the cable without cutting into strength members 14, therebyallowing entry to cavity 20 while inhibiting damage to the at least oneoptical fiber 12 or strength members during the access procedure. Inother words, the craftsman can simply cut into cable jacket 18 byslicing the cable jacket 18 and may use strength members 14 as a guidefor the blade or cutting tool, thereby exposing cavity 20 during thecutting and allowing access to the at least one optical fiber therein.In other words, sizing the cavity minor dimension CH so that it is aboutthe same size or greater than the strength member dimension D that isgenerally aligned with minor dimension H1 advantageously allows quickand reliable access to cavity 20. Thus, the optical fibers in the cablesof the present invention may be easily, quickly, and repeatably accessedby a craftsman or likewise in an automated process. However, cable orcable assembly embodiments according to the present invention can havecavities with minor cavity dimensions generally aligned with the minorcable dimension that are smaller than the strength member dimension D.Additionally, the generally flat major surfaces of the cables areadvantageous because they allow for a smaller cable footprint and usesless jacket material compared with round cables.

Cables according to the present invention may have any suitabledimensions, constructions, and/or fiber counts for the givenapplication. By way of example, in distribution applications the majordimension W1 is preferably about 15 millimeters or less and the minordimension H1 is preferably about 10 millimeters or less. In dropapplications, major dimension W1 is preferably about 10 millimeters orless and the minor dimension H1 is preferably about 5 millimeters orless. Of course, other cables of the present invention can have othersizes and/or structures for the given application depending on therequirements and fiber count of the cable. For instance, cables of thepresent invention may have larger dimensions for the major dimension,the minor dimension, and/or different structures such as a toneableportion as shown in FIG. 5 for locating the cable in buriedapplications. FIG. 13 depicts a cable 300 suitable for aerialapplications that is similar to cable 10 but it further includes amessenger section 330 having a messenger strength member 332. Messengerstrength member 332 is connected with a main cable body 310 by a web 318a of cable jacket 318. Messenger strength member 332 may be formed formany suitable material such as a dielectric or conductor and/or have anysuitable construction such as solid rod or stranded. Additionally, cabledesigns can have any suitable fiber count and/or optical fiberarrangement depending on the application in the optical network. Somesuitable optical fiber arrangements include ribbons with or withoutsubunits, ruggedized ribbons having a tight-buffer layer, tight-bufferedor colored optical fibers, loose optical fibers in a tube, opticalfibers in a module, or optical fibers disposed in a bundle.

Optical fiber ribbons 13 used in the cables of the present invention canhave any suitable design or ribbon count. FIGS. 1 a-1 c depict exemplaryoptical fiber ribbons 13 that use a plurality of subunits each havingfour optical fibers; however, ribbons without subunits are possible andsubunits may have different fiber counts. Subunits allow predeterminedsplitting of the optical fiber ribbons into predictable smaller fibercount units, preferably without the use of special tools. Specifically,each of the depicted ribbons includes six subunits for a total oftwenty-four optical fibers 12, thereby making the illustrated ribbonconfigurations advantageous for a distribution cable. FIG. 1 a depicts atwenty-four fiber ribbon 13 with two twelve-fiber units (not numbered)each having three subunits 13 a connected by secondary matrix 13 b andthe twelve-fiber units are connected together by a common matrix 13 c.FIG. 1 b depicts another similar twenty-four fiber ribbon 13, exceptsubunits 13 a have end portions with a bulbous shape that is at leastpartially disposed over the outboard optical fibers of subunits 13 a asdisclosed in U.S. Pat. Nos. 6,748,148 and 6,792,184. FIG. 1 c depicts atwenty-four fiber ribbon that merely uses subunits 13 a and secondarymatrix 13 b for connecting the subunits together, but secondary matrixfurther includes preferential tear portions (not numbered) forseparating the ribbon into two twelve-fiber units. Of course, othersuitable ribbon configurations are possible such as two twelve fiberunits, three eight fiber units, or six four fiber units depending on therequirements of the network architecture.

Optical fibers preferably have an excess fiber length (EFL) comparedwith a length of cavity 20. For instance, optical fibers have an EFL ofbetween about 0.0 and about 0.5 percent; however, in some instances theEFL may also be slightly negative. Likewise, ribbons can have an excessribbon length (ERL). Besides inhibiting the application of strain to theoptical fibers, EFL or ERL can aid in coupling the optical fibers orribbons with the cable jacket or tube. By way of example, the ERL ispreferably in the range of about 0.1 percent to about 1.2 percent, andmore preferably in the range of about 0.3 percent to about 1.0 percent,and most preferably in the range of about 0.5 percent to about 0.8percent, thereby inhibiting the application of strain, allowing bendingof the fiber optic cable without causing elevated levels of opticalattenuation, and/or suitable low temperature performance. Additionally,the amount of ERL may depend on specific cable design such as the numberof ribbons within the cavity, the cavity size, intended application,and/or other parameters.

As shown in FIG. 1, cavity 20 may be filled with a thixotropic grease orgel (not numbered) to inhibit the migration of water along the same.However, other suitable structures for inhibiting the migration of wateralong the cable are possible. As shown in FIG. 2, cable 10′ is similarto cable 10 but further includes at least one water-swellable yarn 22 orthread disposed longitudinally within cavity 20 for blocking themigration of water. Water blocking structures may also be intermittentalong the cable. For instance, the grease or gel may be disposedintermittently within the cavity or tube. Likewise, intermittent plugsof silicone, foam, or other suitable materials may be used to block themigration of water along the cable.

FIG. 3 depicts a cable 30 that is similar to cable 10 but furtherincludes a plurality of dry inserts 32 (e.g., elongate tapes) such asfoam tapes disposed within the cavity 20 for coupling the ribbons withjacket 18, but dry inserts 32 can also serve for blocking the migrationof water along the cable. As depicted, dry inserts 32 are disposed onboth the top and bottom of the ribbon stack. In other words, thecomponents form a elongate tape/ribbon sandwich with the first elongatetape disposed on a first planar side of the ribbon (or ribbon stack) andthe second elongate tape being disposed on a the second major side ofthe ribbon (or ribbon stack) within the generally rectangular cavity.Stated another way, planar surface(s) of the ribbon generally faces theplanar surface of the dry inserts and the planar surface of the same isalso generally aligned with the major dimension of the cavity so thatall of the major planar surfaces of the components are generally alignedwithin the generally rectangular cavity as depicted in FIG. 3. Ofcourse, other embodiments may have one or more dry inserts wrapped aboutthe optical fibers or disposed on one or more sides thereofSpecifically, cable 30 has two dry inserts 32 formed from an open cellpolyurethane material; however, other suitable materials for couplingand cushioning of the ribbons are possible. In one embodiment, one ormore dry inserts 32 include a water-swellable layer (represented by thesolid hatching of the dry insert) for inhibiting the migration of waterwithin the cable. For instance, a foam layer and a water-swellable layerare laminated together, thereby forming the water-swellable foam tape.In other embodiments, the compressible layer and the water-swellablelayer are discrete individual components that are unattached. Generallyspeaking, water-swellable yarns and/or dry inserts are multi-functional.For instance, besides aiding the coupling the optical fibers, ribbons,or modules to the cable jacket, they may inhibit the migration of water,as well as cushion the optical fibers during bending of the cable.Additionally, dry inserts can be formed from other suitable materialsand/or constructions besides an elongate foam tape for coupling,cushioning and/or allowing movement of the optical fibers . Moreover,like the other dry inserts the water-swellable layer is optional and canuse any suitable material(s)/construction(s).

Illustratively, FIG. 3 a depicts one example of another dry insert 32′.Dry insert 32′ includes a compressible layer formed from a plurality ofmicrospheres 32 b′ disposed between a top tape 32 a′ and bottom tape 32a′. As with other tapes of the dry insert, tapes 32 a′ can be formedfrom any suitable material such as a non-woven material, a polyesterfilm like Mylar, or other like materials. More specifically,microspheres 32 b′ are generally disposed between tapes 32 a′ and areattached using a suitable method such as an adhesive, binding agent,application of heat and/or pressure, or the like. Additionally, anoptional water-swellable substance such as a plurality ofwater-swellable particles, a plurality of water-swellable fiber, or awater-swellable coating 32 c′ may also be disposed between tapes 32 a′with microspheres 32 b′ or on a portion one or more tapes 32 a′.Suitable materials for microspheres 32 b′ are relatively soft so theyare compressible and sized so that they will not cause undue levels ofoptical attenuation if they press against the optical fiber or ribbon.By way of example, suitable hollow microspheres are available from AkzoNobel of the Netherlands under the tradename EXPANCEL and includescopolymers of monomers vinylidene chloride, acrylonitrile, andmethylmethacrylate. Other plastic hollow microspheres are available fromAsia Pacific Microspheres of Malaysia under the tradename of PHENOSET,which are phenolic and amino-based micro spheres.

The compressible nature of hollow polymeric microspheres is suited forproviding adequate coupling of the optical fibers to the tube or cablejacket. Additionally, the smooth round surface of these microspherespermits pressing against the optical fibers without inducing elevatedlevels of optical attenuation such as during bending, twisting, orcrushing of the cable. Additionally, the size of the hollow microspherescan vary from about 1 micron to about 300 microns, likewise, a wallthickness of the microspheres can also vary from about 0.1 micron up toseveral microns, but other suitable dimensions are possible as long as asuitable level of optical performance is maintained.

FIG. 3 b depicts another example of a dry insert 32″ that provides acompressible layer 32 b″ using geometry of its shape. More specifically,compressible layer 32 b″ is provided by using a dimensional fabric thathas a generally textured shape in one or more directions for providingthe compressible layer. As shown, dry insert 32″ has a generallytextured shape TS and is formed from a suitably soft and flexiblematerial so that it can deform for providing an adequate level ofcoupling for the optical fibers or ribbons without causing undue levelsof optical attenuation. By way of example, suitable fabrics areavailable from Freudenberg of Durham, N.C. under the name of Novolon.The dimensional fabrics may be formed from a variety of materials suchas polyester, polypropylene, nylon, or other suitable materials.Generally speaking, dimensional fabrics are formed using a moldingprocess for transforming a two-dimensional (i.e., flat) fabric orsubstrate into a three-dimensional (i.e., textured shape) fabric orsubstrate with the desired textured shape TS. The coupling and/orcompressibility of dry insert 32″ can be tailored by changing parameterssuch as the number of contact points per surface area (i.e., changingthe density of high and low contact points), the height from a highpoint to a low point, the dimension fabric profile, and/or flexibilityof the dimensional fabric. Again, dry insert 32″ can include an optionalwater-swellable layer for blocking the migration of water along thecable or tube assembly. For instance, the water-swellable layer may be acoating applied to one or more surfaces or applied to the fibers of thedimensional fabric, include water-swellable particles disposed in or onthe dry insert, and/or may include superabsorbent fibers. Suitablewater-swellable filaments are, for example, LANSEAL materials availablefrom Toyobo of Osaka, Japan or OASIS materials available from TechnicalAbsorbents Ltd. of South Humberside, United Kingdom.

FIG. 3 c depicts a further embodiment of a dry insert 32′″ having acompressible layer 32 b′″ having a non-woven layer of felt substancemade of one or more materials formed from non-continuous and/orcontinuous filaments. Dry insert 32′″ may optionally include awater-swellable layer and/or one or more tapes for attaching the feltsubstance thereto. For instance, dry insert 32′″ includes a plurality ofwater-swellable filaments 32 a′″ along with other filaments 32 b′″ thatare non-swellable disposed between a plurality of optional tapes 32 c′″,thereby forming dry insert 32′″, As used herein, “felt substance” meansa material comprising one or more types of non-continuous or continuousfilaments and/or fibers which have been caused to adhere and/or matttogether through the action of heat, moisture, chemicals, pressure, ormechanical action such as needle-punching or spun-lacing, or acombination of the foregoing actions, thereby forming a relatively thickand compressible layer. Water-swellable filaments 32 a′″ may compriseany suitable water-swellable material. By way of example, dry insert32′″ of FIG. 3 c may include about 25% or less by weight ofwater-swellable filaments 32 a′″ and about 75% or more by weight ofother filaments 32 b′″; however, other suitable ratios are possible.Other filaments 32 b′″ may include any suitable filament and/or fibermaterial such as polymer filaments like polypropylene, polyethylene, andpolyesters, likewise, other suitable materials such as cottons, nylon,rayons, elastomers, fiberglass, aramids, polymers, rubber-basedurethanes, composite materials and/or blends thereof may be included asa portion of other filaments 32 b′″ and may be tailored for providingspecific characteristics.

FIG. 3 d depicts yet another dry insert 32″″ shaped as a generally flattape having a compressible layer with a suitable width. By way ofexample, dry insert 32″″ is made of a plurality of filaments such as aplurality of generally continuous polyester filaments grouped togetherby a matrix material, but the use of other filament materials ispossible. An optional compressible layer is formed by, for instance,foaming the matrix material, thereby providing a compressible layer 32b″″. In other embodiments, the matrix material is not foamed so itdoesn't provide a compressible layer, but still provides the desiredlevel of coupling. Additionally the matrix material is used forattaching a plurality of water-swellable particles to dry insert 32″″for forming a water-swellable layer 32 a″″. Suitable foamed matrixmaterials include vinyls, polyurethanes, polypropylenes, EVAs, orpolyethylene blends. The plurality of filaments and the matrix materialare run through a die that forms dry insert 32″″ into its desired shapesuch as a generally flat ribbon-like profile. Dry inserts 32″″ may berun parallel to the fiber ribbons in a sandwich configuration or haveother configurations such as helically wrapped about the optical fibersor ribbon stack. Other similar constructions are possible using anysuitable materials for providing the compressible layer and thewater-swellable layer. Dry insert can include still other constructionsand/or materials such as sponge-like materials for a compressible layersuch as polyvinylalcohol (PVA).

No matter the construction and/or materials of the dry insert, fillingmaterial or the like, it should provide a suitable level of coupling forthe optical fibers to the cable jacket. Additionally, in order toquantify the amount of coupling for the optical fibers a relatively longlength of fiber optic cable is required. By way of example, opticalfibers of cables according to the present invention have a couplingforce of at least about 0.1625 Newtons per optical fiber for athirty-meter length of fiber optic cable. Illustratively, a fiber opticcable having a single ribbon with twelve optical fibers in the ribbonshould have a minimum coupling force of about 1.95 Newtons for athirty-meter length of fiber optic cable. Likewise, a similar fiberoptical cable having a single optical fiber ribbon with six opticalfibers should have a minimum coupling force of about 0.975 Newtons for athirty-meter length of fiber optic cable. Measurement of the couplingforce is accomplished by taking a thirty-meter fiber optic cable sampleand pulling on a first end of the optical fibers (or fiber opticribbon(s)) and measuring the force required to cause movement of thesecond end of the optical fiber(s) (or fiber optic ribbon(s)). In otherwords, the EFL (or ERL) must be straightened so that the coupling forceis the amount of force required to move the entire length of opticalfibers within the thirty-meter fiber optic cable sample.

FIG. 4 depicts a cable 40 similar to cable 10 that has a plurality ofoptical fiber modules 15 instead of ribbons 13. Optical fiber modules 15organize and protect the plurality of optical fibers 12 within eachmodule jacket 15 a. Consequently, optical fiber modules 15 can be routedout of the cavity of cable 40 while still having a protective coveringdisposed about the optical fibers. By way of example, each optical fibermodule 15 includes twelve colored optical fibers 12, thereby forming arelatively high optical fiber packing density. Moreover, optical fibermodule 15 allows access to individual optical fibers within the modulejacket 15 a without having to remove the same from a ribbon matrixmaterial. Preferably, module jacket 15 a is formed from a material thatis easily tearable without tools. For instance, module jacket 15 a isformed from a highly filled material so that it is easily tearable bythe craftsman merely using his fingers to tear the same and it will notstick to colored or tight-buffered optical fibers. Suitable modulejacket materials may include a polybutylene terephthalate (PBT), apolycarbonate and/or a polyethylene (PE) material and/or an ethylenevinyl acrylate (EVA) or other blends thereof having fillers like a chalkor talc; however, other suitable materials are possible such as aUV-curable acrylate. Modules 15 may include other suitable componentssuch as a grease, water-swellable yarn, suitable thread or tape, aripcord, or other suitable component. Additionally, the cavity of cable40 may include a grease, water-swellable yarn or tape, dry insert,and/or any other suitable component.

FIG. 5 depicts a fiber optic cable 50 that is similar to cable 10, butit further includes a tube 52 having a generally rectangularcross-section within the cavity and a toneable lobe 55. Tube 52 providesfurther protection for optical fibers 12 when opening the cavity.Moreover, since optical fibers 12 remain within a protective structureafter the cavity of the cable is opened, i.e., tube 52, module or thelike, the optical fibers may be routed and stored while still beingprotected. By way of example, when the cable is routed into a closure aportion of jacket 18 is removed and strength members 14 are cut to anappropriate length so they can be strain relieved, thereafter tube 52having optical fibers 12 therein can be routed within the closure whilebeing protected and the protective structure can be removed or openedwhen required. In this embodiment, tube 52 provides the freespace thatallows fiber movement. Additionally, the material for tube 52 may beselected for providing predetermined friction properties for tailoringthe coupling level between the optical fibers, ribbons, modules, or thelike.

Cable 50 also includes toneable lobe 55 that is useful for locating thecable in buried applications while still allowing for a main cable body51 that is dielectric. Toneable lobe 55 includes a conductive wire 57disposed within a jacket portion 58 of toneable lobe 55. By way ofexample, conductive wire 57 is a 24-gauge copper wire that allows thecraftsman to apply a toning signal thereto for locating the cable so itcan be located or have its location marked to prevent inadvertentdamage. Jacket 18 and jacket portion 58 are typically co-extrudedsimultaneously using the same extrusion tooling. As shown, jacketportion 58 is connected with jacket 18 of main cable body 51 by afrangible web 59 so that toneable lobe 55 can easily be separated frommain cable body 51 for connectorization or other purposes. Specifically,web 59 can include a preferential tear portion (not numbered) usingsuitable geometry for controlling the location of the tear between thetoneable lobe 55 and main cable body 51. Toneable lobe 55 preferablytears away from main cable body 51 cleanly so that it does not leave aridge thereon, thereby allowing for a profile that permits easy sealingwith a connector boot or the like. Toneable lobe 55 is advantageousbecause if the cable is struck by lightning the toneable lobe 55 wouldbe damaged, but main cable body 51 would not be significantly damagedsince it is dielectric. Consequently, the cable is toneable withoutrequiring the labor and hardware necessary for grounding the cable. Ofcourse, other cables of the present invention may also include atoneable lobe.

FIG. 6 depicts another cable 60 similar to cable 10 which furtherincludes at least one preferential tear portion 62 for separating one ormore of the strength members 14 from a medial portion 64 of cable 60. Asdepicted, cable 60 includes four preferential tear portions 62 disposedbetween a respective strength member 14 and medial portion 64.Consequently, each respective strength member 14 along with a portion ofjacket 18 may be separated from medial portion 64 of cable 60 by theapplication of a sufficient separation force. Preferential tear portions62 are advantageous because they allow optical fibers 12 to have aprotective structure without using a module or tube. In other words, theportion of jacket 18 that remains after separating strength members 14from medial portion 64 acts as a protective structure for the opticalfibers. Additionally, cable 60 includes more than two optical fiberribbons 13, thereby yielding a relatively high fiber count fordistribution.

FIG. 7 depicts still another cable 70 according to the present inventionthat includes a plurality of cavities 20 a,20 b for housing opticalfibers. Using more than one cavity allows for flexibility in the cableapplications. Multiple cavities can have similar or different sizes thatare suited for the particular application. As shown, cavities 20 a,20 bhave similar minor dimensions, but have different major dimensions,thereby allowing different ribbon fiber counts in respective cavities.Specifically, cavity 20 a is sized for a plurality of 4-fiber ribbons 13a that can be accessed for distribution along the cable and then routedtoward the subscriber and cavity 20 b is sized for a plurality of12-fiber ribbons 13 b that are intended to run the entire length of thecable. Other embodiments are possible, for instance, a first cavity canhave modules with 4-fibers and a second cavity can have modules with12-fibers. FIG. 7 also illustrates an optional strength member 14disposed between cavities 20 a and 20 b. The optional strength member isadvantageous if it desired to only access one of the cavities whenopening the cable by allowing a stopping point and/or a guide for thecutting tool. The optional strength member may be the same size as theoutboard strength members or it may have a different size. Moreover, theoptional strength member may have a shape other than round so that themajor cable dimension may be minimized. Other structures may be used foraiding in opening only one of multiple cavities. For instance, FIG. 7 adepicts a cable 70′ having cavities 20 a′ and 20 b′ that are offsetrelative to plane A-A that passes through the center points of strengthmembers 14. Specifically, cavity 20 a′ is offset towards the bottommajor surface of the cable for access from that surface and cavity 20 b′is offset towards the top major surface of the cable for access fromthat surface. Simply stated, the cavity having the four fiber ribbons iseasily accessible from one major surface and the cavity having thetwelve fiber ribbons is easily accessible from the other major surface.Moreover, one or more of the major surfaces may be marked (not visible)to indicate which cavity is accessible from the given surface. Ofcourse, other cables configurations of the present invention can usemore than one cavity.

FIG. 8 illustrates a fiber optic cable 80 that includes at least onearmored component 85 that provides rodent protection and/or additionalcrush strength for the cable. Specifically, cable 80 includes at leastone optical fiber 12 disposed within a tube 82 that has strength members14 disposed on opposite ends thereof, two armor components 85 aredisposed about tube 82, and jacket 18 is applied thereover. Armorcomponents 85 may be formed from any suitable material such as adielectric such as a high-strength polymer or a conductive material suchas a steel tape. Moreover, the armor components may be, shaped, ribbed,corrugated or the like for improving its crush strength and/or flexuralperformance of the cable. In this embodiment, armor components 85 haverespective curved end portions that generally contact each strengthmember 14 so that any crush forces are directed and/or transferredtowards the same. Additionally, if a conductive armor component is used,strength members 14 are preferably also formed from a conductivematerial such as steel, rather than a more expensive glass-reinforcedplastic strength member. Moreover, it is also possible to join or attachstrength member 14 with the armor layer by gluing, crimping, welding, orthe like. FIG. 8 a depicts a cable 80′ having a pair of generally flatarmor components 85 disposed within the cable jacket. The cable jacketof this embodiment is formed from more than one layer, specifically aninner jacket 18′ and an outer jacket 18″. Consequently, the propertiesmay be tailored for performance such as coupling, tear resistance, orthe other properties. By way of example, inner jacket 18′ may be alinear low-density polyethylene (LLDPE) for tear resistance and outerjacket 18″ may be a medium or high density polyethylene for durabilityand abrasion resistance; however, other suitable materials may be used.In this embodiment, the cavity does not include a tube therein and theminor cavity dimension is smaller than the strength member dimension.Additionally, cable 80′ includes a plurality of optional ripcords 89disposed between armor components 85′ and strength members 14.

Cables of the present invention are also useful as a portion of a largercable assembly that is useful for distributing optical fibers toward thesubscriber. The cable assemblies can be assembled in the factory or theycan be constructed in the field. FIGS. 9 and 10 respectively depictperspective and cross-sectional views of an exemplary cable assembly 100that is suitable for distributing optical fiber(s) towards thesubscriber in a communication network. Cable assembly 100 includes adistribution cable 110, which may be similar to cable 10, and a tethercable 130 that can be used for connecting to a node of the opticalnetwork. In preferred embodiments, a plurality of tether cables 130 haveat least one optical fiber in optical communication with optical fibersof distribution cable 110 so that the cable assembly can connect to aplurality of nodes. Cable assemblies of the present invention can useany suitable distribution and/or tether cables as dictated by the givenapplication. As shown, distribution cable 110 includes at least oneoptical fiber that is a portion of optical fiber ribbon 113, at leastone strength member 114, and a cable jacket 118. Cable jacket 118 formsa cavity 120 therein for housing optical fiber 112. Like cable 10,cavity 120 has a cavity minor dimension CH and a cavity major dimensionCW. Again, cavity minor dimension CH is generally aligned with a minordimension H1 of distribution cable 110 and cavity major dimension CW isgenerally aligned with the major dimension W1 of distribution cable 110.As depicted, distribution cable 110 strength members 114 are disposed onopposite sides of cavity 120 and are sized so that a strength memberdimension D is about the same size or smaller than the cavity minordimension CH, but other suitable geometries are possible. Consequently,the craftsman in the factory or the field has simple and easy access tocavity 120, thereby allowing entry to cavity 120 while inhibiting damageto the at least one optical fiber 112 and/or strength members 114 duringthe access procedure.

FIG. 10 a is a perspective view showing distribution cable 110 after itis opened with tether cable 130 prepared and in position before beingwrapped by a tape (not shown) and encapsulated by a sealing portion 140such as overmolded portion, heat-shrink tubing or the like. As shown,the appropriate optical fibers of tether cable 130 are opticallyconnected with the appropriate optical fibers of distribution cable 110and the routing of fibers and the optical connection are protected fromundue stresses using suitable structures and/or components duringbending. Preparing tether cable 130 for assembly 100 optionally includesremoving a portion of the jacket 138 of tether cable 130 and optionallyexposing the strength members 134 and as shown. A portion of strengthmembers 134 are exposed so that they can be connected and/or secured bythe sealing portion 140, thereby providing strain relief for tethercable 130. Thereafter, the optical fibers (not numbered) of tether cable130 may be enclosed in a respective furcation tubing (not numbered) forprotecting and routing the fibers towards a splice point 125. Theoptical fibers are fusion spliced together and splice point 125 may beoptionally held in a splice holder, furcation tube, or the like and maygenerally disposed within an opened portion of the cavity 120 of thedistribution cable. Positioning splice point 125 within cavity 120 isadvantageous because it is disposed relatively close to a neutralbending axis of cable assembly 100, thereby inhibiting stresses onsplice point 125 during bending of cable assembly 100. Additionally, thesplice holder and a portion of the furcation tubes may optionally beenclosed within a small tube for further protection and/or allowingsmall movement among the components. Of course, other constructions arepossible such as locating the splice outward of the distribution cableand using an indexing tube with the tether cable for preloading anexcess fiber length into the tether optical fiber. Then, about the pointwhere the optical connection between the cables is performed anenvironmental seal is provided to seal out the elements and inhibitbending beyond a minimum bend radius. By way of example, the area aboutthe connection point of the cables includes sealing portion 140 formedfrom a suitable material, but other suitable sealing configurations arepossible. Before applying a sealing portion 140 such as overmolding orheat shrink tubing, an optional protective tape or wrap is applied overthe splice area for keeping the overmold material away from sensitiveareas. The cross-sectional footprint of sealing portion 140 should berelatively small and straightforward to construct while providing thenecessary protection. Additionally, tether cable 110 may further includea ferrule 139 and/or a connector (not shown) on its free-end for quickand easy connection to the optical network. In assemblies intended foroutdoor applications the connector is preferably environmentally sealedand hardened, thereby making it robust and reliable. An example of asuitable connector is available from Corning Cable Systems sold underthe tradename OptiTap; however, other suitable connectors may be used.

Tether cable 120 can have any suitable cable construction such as roundor generally flat as shown in FIG. 9; however, a generally flat designmay have advantages. Because cable assembly 100 uses two generally flatcables it imparts a relatively small cable assembly cross-sectionalfootprint with adequate flexibility, thereby making the assemblyadvantageous in certain applications such as pulling into ducts wheresmall footprints and flexibility are required. For instance, smallsuitable cross-section footprints such as in FIG. 9 makes pulling thecable assembly into ducts such as 1¼ inch inner diameter ductsrelatively easy. Respectively, FIGS. 11 a and 11 b schematically depicta cross-section of cable assembly 100 disposed in a 1¼ inch innerdiameter duct and a cross-section of a cable assembly 150 using a rounddistribution cable for comparative purposes. As shown, cable assembly100 has a relatively small duct fill ratio that allows for easilypulling of the assembly. Besides the fill ratio, the maximum assemblycross-sectional dimension is also important when pulling into duct. Asshown by FIG. 11, cable assembly 100 has a relatively small maximumassembly cross-sectional dimension because the major dimensions of thecables are generally parallel and the minor dimensions are generallystacked together. Consequently, cable assembly 100 is suitable foraerial, buried, or duct applications. On the other hand, cable assembly150 uses a round distribution cable and has a relatively large fillratio and maximum assembly cross-sectional dimension, thereby makingpulling around bends and corners in duct difficult if not impossible ifthe assembly fits within the duct.

Cable assembly 100 has a maximum cross-sectional area near the pointwhere tether cable 130 is connected due to the connectorization and/orenvironmentally sealing, (i.e., the overmolding), near the point wherethe distribution cable is opened. For instance, at the sealing portion140, cable assembly 100 preferably has a maximum assemblycross-sectional dimension of about 25 millimeters or less, morepreferably, about 21 millimeters or less, and most preferably about 17millimeters or less. Additionally, cable assemblies of present inventionhave a fill-ratio about 80 percent or less and more preferably about 70percent or less for the given inner diameter of the duct.

FIGS. 12 and 12 a respectively illustrate a cross-sectional view and aperspective view of a cable assembly 200 that includes a distributioncable 210, a receptacle or other suitable joining point 230, and asealing portion 240 such as an overmold portion or the like. Cableassembly 200 is advantageous because it has a relatively smallcross-sectional footprint due to the arrangement between distributioncable 210 and receptacle 230. Distribution cable 210 includes aplurality of ribbons 213 disposed within a cavity 220 of a cable jacket218. Distribution cable 210 also includes two strength members 214disposed on opposite sides of cavity 220. Distribution cable 210 has aflat profile with two generally flat major surfaces (not numbered) withmajor dimension W2 and minor dimension H2 of the cable; however, thiscable may have any suitably sized and/or shaped cavity. Simply stated,cavity 220 may have any suitable minor or major dimension. In thisembodiment, cable assembly 200 routes the optical fibers from one ormore of the plurality of ribbons 213 of distribution cable 210 toreceptacle 230 without using a tether cable. As shown, this embodimentincludes twelve-fiber ribbons and uses twelve-fiber ferrules; however,any suitable combination of optical fiber arrangements and ferruleconstructions are possible. Receptacle 230 is suitable for terminating aplurality of optical fibers 212 within a multifiber ferrule 232 that isattached to housing 234 of the receptacle. Receptacle 230 is preferablyhardened and configured for an environmental sealing of the assembly.Housing 234 aids in aligning and protecting ferrule 232 and ispreferably keyed. Additionally, receptacle 230 may have a threadedportion for securing the optical connection with a complimentary matingassembly such as a hardened connector. Additionally, receptacle 230 canhave a cap 250 that is removably attached thereto for protecting theferrule, connector, and/or receptacle during sealing such as withovermolding and afterwards. Suitable receptacles are shown and describedin U.S. Pat. No. 6,579,014 issued Jun. 17, 2003 entitled “Fiber OpticReceptacle” and U.S. patent application No. 10/924,525 filed Aug. 24,2004 entitled “Fiber Optic Receptacle and Plug Assemblies”. Other cableassemblies may have connectors or receptacles that eliminate the shroudor housing, thereby allowing a smaller cross-sectional footprint.Specifically, optical fibers 212 are routed to a multifiber ferrule 232of connector 230 where they are attached in respective bores. Ferrule232 has a cross-section with a minor axis FH and a major axis FW.Ferrule 232 may have any suitable orientation with respect to cable 210,but in preferred embodiments minor axis FH is generally aligned withminor dimension H2 of cable 210, thereby providing a known orientationthat may be useful for maintaining a small cross-sectional footprint forthe assembly. Of course, cable assembly 200 can have multiple connectors230 attached along its length; moreover, cable assembly 200 may locateconnectors on either or both sides of the generally flat major surfaces.

The cables of the present invention may also use optical fibers that arerelatively bend resistant for preserving optical performance whensubjected to relatively small bend radii. FIG. 14 depicts arepresentation of a bend performance optical fiber 12′ suitable for usein fiber optic cables, cables assemblies, fiber optic hardware and othernetwork components of the present invention. For instance, cable 30using a bend performance optical fiber has relatively small deltaattenuation when coiled into a relatively small bend radius. By way ofexample, when bent into a coil having a single turn with a diameter ofabout 200 millimeters (i.e., a radius of about 100 millimeters) opticalfibers of cable 30 have a delta optical attenuation of about 0.1 dB orless per turn, and more preferably about 0.03 dB or less per turn,thereby preserving suitable levels of optical performance for the cable.For instance, slack storage of several turns such as 3 or more turns ofcable 30 into a coil having a diameter of about 200 millimeters wouldresult in the delta optical attenuation of about 0.4 dB or less.

By way of example, bend resistant optical fibers may havemicrostructures that allow reduced bend radii while preserving opticalperformance, thereby permitting aggressive bending/installationsolutions while optical attenuation remains extremely low. As shown,bend performance optical fiber 12′ is a microstructured optical fiberhaving a core region and a cladding region surrounding the core region,the cladding region comprising an annular hole-containing regioncomprised of non-periodically disposed holes such that the optical fiberis capable of single mode transmission at one or more wavelengths in oneor more operating wavelength ranges. The core region and cladding regionprovide improved bend resistance, and single mode operation atwavelengths preferably greater than or equal to 1500 nm, in someembodiments also greater than about 1310 nm, in other embodiments alsogreater than 1260 nm. The optical fibers provide a mode field at awavelength of 1310 nm preferably greater than 8.0 microns, morepreferably between about 8.0 and 10.0 microns. In preferred embodiments,optical fiber disclosed herein is thus single-mode transmission opticalfiber.

In some embodiments, the microstructured optical fibers disclosed hereincomprises a core region disposed about a longitudinal centerline, and acladding region surrounding the core region, the cladding regioncomprising an annular hole-containing region comprised ofnon-periodically disposed holes, wherein the annular hole-containingregion has a maximum radial width of less than 12 microns, the annularhole-containing region has a regional void area percent of less thanabout 30 percent, and the non-periodically disposed holes have a meandiameter of less than 1550 nm.

By “non-periodically disposed” or “non-periodic distribution”, we meanthat when one takes a cross-section (such as a cross-sectionperpendicular to the longitudinal axis) of the optical fiber, thenon-periodically disposed holes are randomly or non-periodicallydistributed across a portion of the fiber. Similar cross sections takenat different points along the length of the fiber will reveal differentcross-sectional hole patterns, i.e., various cross-sections will havedifferent hole patterns, wherein the distributions of holes and sizes ofholes do not match. That is, the holes are non-periodic, i.e., they arenot periodically disposed within the fiber structure. These holes arestretched (elongated) along the length (i.e. in a direction generallyparallel to the longitudinal axis) of the optical fiber, but do notextend the entire length of the entire fiber for typical lengths oftransmission fiber.

For a variety of applications, it is desirable for the holes to beformed such that greater than about 95% of and preferably all of theholes exhibit a mean hole size in the cladding for the optical fiberwhich is less than 1550 nm, more preferably less than 775 nm, mostpreferably less than 390 nm. Likewise, it is preferable that the maximumdiameter of the holes in the fiber be less than 7000 nm, more preferablyless than 2000 nm, and even more preferably less than 1550 nm, and mostpreferably less than 775 nm. In some embodiments, the fibers disclosedherein have fewer than 5000 holes, in some embodiments also fewer than1000 holes, and in other embodiments the total number of holes is fewerthan 500 holes in a given optical fiber perpendicular cross-section. Ofcourse, the most preferred fibers will exhibit combinations of thesecharacteristics. Thus, for example, one particularly preferredembodiment of optical fiber would exhibit fewer than 200 holes in theoptical fiber, the holes having a maximum diameter less than 1550 nm anda mean diameter less than 775 nm, although useful and bend resistantoptical fibers can be achieved using larger and greater numbers ofholes. The hole number, mean diameter, max diameter, and total void areapercent of holes can all be calculated with the help of a scanningelectron microscope at a magnification of about 800× and image analysissoftware, such as ImagePro, which is available from Media Cybernetics,Inc. of Silver Spring, Md., USA.

The optical fibers disclosed herein may or may not include germania orfluorine to also adjust the refractive index of the core and or claddingof the optical fiber, but these dopants can also be avoided in theintermediate annular region and instead, the holes (in combination withany gas or gases that may be disposed within the holes) can be used toadjust the manner in which light is guided down the core of the fiber.The hole-containing region may consist of undoped (pure) silica, therebycompletely avoiding the use of any dopants in the hole-containingregion, to achieve a decreased refractive index, or the hole-containingregion may comprise doped silica, e.g. fluorine-doped silica having aplurality of holes.

In one set of embodiments, the core region includes doped silica toprovide a positive refractive index relative to pure silica, e.g.germania doped silica. The core region is preferably hole-free. Asillustrated in FIG. 14, in some embodiments, the core region 170comprises a single core segment having a positive maximum refractiveindex relative to pure silica Δ₁ in %, and the single core segmentextends from the centerline to a radius R₁. In one set of embodiments,0.30%<Δ₁<0.40%, and 3.0 μm<R₁<5.0 μm. In some embodiments, the singlecore segment has a refractive index profile with an alpha shape, wherealpha is 6 or more, and in some embodiments alpha is 8 or more. In someembodiments, the inner annular hole-free region 182 extends from thecore region to a radius R₂, wherein the inner annular hole-free regionhas a radial width W12, equal to R2−R1, and W12 is greater than 1 μm.Radius R2 is preferably greater than 5 μm, more preferably greater than6 μm. The intermediate annular hole-containing region 184 extendsradially outward from R2 to radius R3 and has a radial width W23, equalto R3−R2. The outer annular region 186 extends radially outward from R3to radius R4. Radius R4 is the outermost radius of the silica portion ofthe optical fiber. One or more coatings may be applied to the externalsurface of the silica portion of the optical fiber, starting at R4, theoutermost diameter or outermost periphery of the glass part of thefiber. The core region 170 and the cladding region 180 are preferablycomprised of silica. The core region 170 is preferably silica doped withone or more dopants. Preferably, the core region 170 is hole-free. Thehole-containing region 184 has an inner radius R2 which is not more than20 μm. In some embodiments, R2 is not less than 10 μm and not greaterthan 20 μm. In other embodiments, R2 is not less than 10 μm and notgreater than 18 μm. In other embodiments, R2 is not less than 10 μm andnot greater than 14 μm. Again, while not being limited to any particularwidth, the hole-containing region 184 has a radial width W23 which isnot less than 0.5 μm. In some embodiments, W23 is not less than 0.5 pmand not greater than 20 μm. In other embodiments, W23 is not less than 2μm and not greater than 12 μm. In other embodiments, W23 is not lessthan 2 μm and not greater than 10 μm.

Such fiber can be made to exhibit a fiber cutoff of less than 1400 nm,more preferably less than 1310 nm, a 20 mm macrobend induced loss at1550 nm of less than 1 dB/turn, preferably less than 0.5 dB/turn, evenmore preferably less than 0.1 dB/turn, still more preferably less than0.05 dB/turn, yet more preferably less than 0.03 dB/turn, and even stillmore preferably less than 0.02 dB/turn, a 12 mm macrobend induced lossat 1550 nm of less than 5 dB/turn, preferably less than 1 dB/turn, morepreferably less than 0.5 dB/turn, even more preferably less than 0.2dB/turn, still more preferably less than 0.01 dB/turn, still even morepreferably less than 0.05 dB/turn, and a 8 mm macrobend induced loss at1550 nm of less than 5 dB/turn, preferably less than 1 dB/turn, morepreferably less than 0.5 dB/turn, and even more preferably less than 0.2dB-turn, and still even more preferably less than 0.1 dB/turn.

An example of a suitable fiber is illustrated in FIG. 15. The fiber inFIG. 15 comprises a core region that is surrounded by a cladding regionthat comprises randomly disposed voids which are contained within anannular region spaced from the core and positioned to be effective toguide light along the core region. Other optical types of bendperformance optical fibers and/or microstructured fibers may be used inthe present invention. Additional description of microstructured fibersused in the present invention are disclosed in pending U.S. patentapplication Ser. No. 11/583,098 filed Oct. 18, 2006; and, ProvisionalU.S. patent application Ser. Nos. 60/817,863 filed Jun. 30, 2006;60/817,721 filed Jun. 30, 2006; 60/841,458 filed Aug. 31, 2006; and60/841,490 filed Aug. 31, 2006; all of which are assigned to CorningIncorporated; and incorporated herein by reference.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the cable and cableassemblies of the present invention without departing from the spirit orscope of the invention. For instance, cables or assemblies of thepresent invention can include other cable components such as ripcords,paper or mica tapes, a friction element, or other suitable components.Illustratively, a cable similar to cable 10 can further include aplurality of small steel wires disposed near the north and southpositions for inhibiting cutting into the grps during access procedures.Although cable assemblies discuss a distribution cable that is inoptical communication with one or more tether cables, the cableassemblies may be used upstream in the optical network such as a feedercable that is in optical communication with one or more distributioncables. Thus, it is intended that the present invention cover themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

1. A fiber optic cable assembly comprising: a dry distribution cablehaving: (a) at least one optical fiber; (b) at least one strengthmember; and (c) a cable jacket, the cable jacket having a cavity,wherein the at least one optical fiber is disposed within the cavity,and the at least one optical fiber having a predetermined level ofcoupling to the cable jacket, wherein the predetermined level ofcoupling is about 0.1625 Newtons or more per optical fiber for a thirtymeter length of the dry distribution cable; and a tether optical fibercable, the tether optical fiber cable having at least one tether opticalfiber, the at least one tether optical fiber being in opticalcommunication with the at least one optical fiber of the drydistribution cable.
 2. The fiber optic cable assembly of claim 1,further comprising a sealing portion that provides an environmental sealbetween the dry distribution cable and the tether cable.
 3. The fiberoptic cable assembly of claim 2, further comprising a ferrule attachedto the at least one tether optical fiber.
 4. The fiber optic cableassembly of claim 1, further comprising a ferrule attached to the atleast one tether optical fiber.
 5. The fiber optic cable assembly ofclaim 1, further comprising a multifiber ferrule attached to the atleast one tether optical fiber, the multifiber ferrule comprising aportion of a connector.
 6. The fiber optic cable assembly of claim 1,further comprising a ferrule attached to the at least one tether opticalfiber, wherein the ferrule is a portion of a connector that includes ashroud.
 7. The fiber optic cable assembly of claim 1, further comprisinga multifiber ferrule attached to the at least one tether optical fiber.8. The fiber optic cable assembly of claim 7, wherein the cavity isgenerally rectangular.
 9. The fiber optic cable assembly of claim 1,wherein the cavity is generally rectangular.
 10. The fiber optic cableassembly of claim 1, further comprising at least two strength membersthat are disposed on opposite sides of the cavity of the drydistribution cable.
 11. The fiber optic cable assembly of claim 10,wherein the cavity is generally rectangular.
 12. The fiber optic cableassembly of claim 1, the at least one optical fiber being a portion of afiber optic ribbon.
 13. The fiber optic cable assembly of claim 12,wherein the cavity is generally rectangular.
 14. The fiber optic cableassembly of claim 12, wherein the fiber optic ribbon is splitable intosubunits.
 15. The fiber optic cable assembly of claim 1, the at leastone optical fiber of the dry distribution cable being a portion of amodule, the module having a sheath.
 16. The fiber optic cable assemblyof claim 15, further comprising a water-swellable component or awater-blocking component.
 17. The fiber optic cable assembly of claim 1,further comprising a water-swellable component or a water-blockingcomponent.
 18. The fiber optic cable assembly of claim 1, furthercomprising a tube disposed within the cavity.
 19. The fiber optic cableassembly of claim 1, further including at least one dry insert disposedwithin the cavity for coupling the at least one optical fiber with thecable jacket.
 20. The fiber optic cable assembly of claim 19, whereinthe cavity is generally rectangular.
 21. The fiber optic cable assemblyof claim 1, the cavity being offset from an plane A-A so that it iscloser to one of the two major surfaces than the other major surface,wherein plane A-A is defined by the center points of a pair of strengthmembers that are disposed on opposite side of the cavity.
 22. The fiberoptic cable assembly of claim 21, wherein the cavity is generallyrectangular.